Because any velocity I ascribe to a particle or an object, you will add a certain constant to it by the law of composition of velocity.

因为我描述的任何一个质点或者物体的速度,你都要根据速度叠加法则,给它加上某个常数

耶鲁公开课 - 基础物理课程节选

But the law of composition is not always commutative.

但是两两结合的运算并不总是可交换的

耶鲁公开课 - 基础物理课程节选